While i understand what Dr. Sproul is getting at, this is an unfortunate statement. Something from nothing is not irrational, it is indeed, how the creation came about, and no one has ever successfully accused God of irrationality! It would have been better to say that for finite, limited human beings, it is something from nothing, which is irrational...ex nihilo, nihilo fit only applies to the creation, not the Creator.
I would agree in the case of God's creative power. He created the Universe from nothing. But in the case above we're addressing human will. Indeed, does not God's will (at least as far as we're concerned) also operate by the same principle as ours insofar as God does not make random choices but rather those according to His desires (which, fortunately for us, happen to be immutably good)?